1. Field of the Invention
Aspects of the present invention relate to a method of decoding a binary image at high speed, and more particularly to a method of decoding a binary image at a high speed during a pixel decoding process of a Joint Bi-level Image Experts Group (JBIG).
2. Description of the Related Art
JBIG is an international standard of a binary-image compression algorithm from the Joint Bi-level Image Experts Group. The JBIG algorithm is based on an arithmetic coding process. Specifically, context data appears in the form of a peripheral pattern at each pixel of the corresponding image, and is used to search for a statistical prediction indicating which of the pixels are white or black.
The JBIG decoding process uses a context value defined in 10 bits including neighboring pixel information that has already been decoded. The JBIG decoding process calculates a Less Probable Symbol Size (LSZ) value and a More Probable Symbol (MPS) value, estimates a current pixel using the LSZ and MPS values, and decodes the estimated result. In this case, the LSZ value is indicative of status information calculated by the above-mentioned context value, and the MPS value is indicative of another value calculated by the above-mentioned context value.
However, the conventional system has a sequential structure in pixel units (i.e., 1 pixel or 1 clock units), such that the speed of the conventional system is fixed according to images. For example, if the image is all in white, the horizontal size of the image is 10000 pixels, and the vertical size of the image is 10000 pixels, then the image data is compressed over a time period corresponding to (10000×10000) clocks even though the code size is relatively small.
Therefore, because the conventional system performs calculations in pixel units, the execution speed is slow, uses time to process overlapped parts such as blanks, and decreases a decoding speed.